Secreted frizzled-related protein-1 inhibits RANKL-dependent osteoclast formation

Häusler, Karl D, Horwood, Nicole J, Chuman, Yoshiro, Fisher, Jane L, Ellis, Jennifer, Martin, T John, Rubin, Jeffrey S and Gillespie, Matthew T (2004) Secreted frizzled-related protein-1 inhibits RANKL-dependent osteoclast formation. Journal of Bone and Mineral Research, 19 (11). pp. 1873-1881. ISSN 0884-0431

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Abstract

UNLABELLED: We determined that sFRP-1 mRNA was differentially expressed by osteoblast/stromal cell lines and that sFRP-1 neutralizing antibodies and siRNA complementary to sFRP-1 coding sequence enhanced, while recombinant sFRP-1 inhibited, osteoclast formation. In studying the mechanism of action for sFRP-1, we found that sFRP-1 could bind recombinant RANKL. These results suggest potential cross-talk between Wnt and RANKL pathways. INTRODUCTION: Osteoclast formation in normal bone remodeling requires the presence of osteoblast lineage cells that express RANKL and macrophage-colony-stimulating factor (M-CSF), which interact with their cognate receptors on the osteoclast precursor. We identified secreted Frizzled-related protein-1 (sFRP-1), which is known to bind to Wnt and inhibit the Wnt signaling pathway, as an osteoblast-derived factor that impinges on osteoclast formation and activity. MATERIALS AND METHODS: Differential display of mRNA from osteoblast lineage cell lines established sFRP-1 to be highly expressed in an osteoclast supporting cell line. sFRP-1 expression in bone was determined by in situ hybridization, and the effects of sFRP-1 on osteoclast formation were determined using a neutralizing antibody, siRNA, for sFRP-1 and recombinant protein. RESULTS: In situ hybridization revealed sFRP-1 mRNA expression in osteoblasts and chondrocytes in murine bone. sFRP-1 mRNA expression could be elevated in calvarial primary osteoblasts in response to prostaglandin E2 (PGE2) or interleukin (IL)-11, whereas many other osteotropic agents (e.g., IL-1, IL-6, calcitrol, parathyroid hormone) were without any effect. In vitro assays of osteoclast formation established sFRP-1 to be an inhibitor of osteoclast formation. Neutralizing antibodies against sFRP-1 enhanced TRACP+ mononuclear and multinuclear osteoclast formation (3- and 2-fold, respectively) in co-cultures of murine osteoblasts with spleen cells, whereas siRNA complementary to sFRP-1 coding sequence significantly enhanced osteoclast formation in co-cultures of KUSA O (osteoblast/stromal cell line) and bone marrow cells, cultured in the presence of PGE2 and 1,25(OH)2 vitamin D3. Recombinant sFRP-1 dose-dependently inhibited osteoclast formation in osteoblast/spleen co-cultures, RANKL + M-CSF-treated splenic cultures, and RANKL-treated RAW264.7 cell cultures, indicating a direct action of sFRP-1 on hematopoietic cells. Consistent with this, sFRP-1 was found to bind to RANKL in ELISAs. CONCLUSION: sFRP-1 is expressed by osteoblasts and inhibits osteoclast formation. While sFRP-1 activity might involve the blocking of endogenous Wnt signaling, our results suggest that, alternatively, it could be because of direct binding to RANKL. This study describes a new mechanism whereby osteoblasts regulate osteoclastogenesis through the expression and release of sFRP-1.

Item Type: Article
Uncontrolled Keywords: animals,metabolism,metabolism,metabolism,antagonists & inhibitors,cell line,metabolism,dose-response relationship, drug,enzyme-linked immunosorbent assay,metabolism,gene expression profiling,gene expression regulation,metabolism,in situ hybridization,metabolism,metabolism,metabolism,metabolism,male,antagonists & inhibitors,metabolism,mice,mice, inbred c57bl,metabolism,metabolism,metabolism,polymerase chain reaction,rank ligand,metabolism,metabolism,receptor activator of nuclear factor-kappa b,metabolism,chemistry,signal transduction,wnt proteins
Faculty \ School: Faculty of Medicine and Health Sciences > Norwich Medical School
Depositing User: LivePure Connector
Date Deposited: 06 Mar 2019 10:30
Last Modified: 22 Apr 2020 07:34
URI: https://ueaeprints.uea.ac.uk/id/eprint/70127
DOI: 10.1359/JBMR.040807

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